light pipe ⇝

optical fibre

(fibre optics, FO, US "fiber", light pipe) A
plastic or glass (silicon dioxide) fibre no thicker than a
human hair used to transmit information using infra-red or
even visible light as the carrier (usually a laser). The
light beam is an electromagnetic signal with a frequency in
the range of 10^14 to 10^15 Hertz.

Optical fibre is less susceptible to external noise than other
transmission media, and is cheaper to make than copper wire,
but it is much more difficult to connect. Optical fibres are
difficult to tamper with (to monitor or inject data in the
middle of a connection), making them appropriate for secure
communications. The light beams do not escape from the medium
because the material used provides total internal reflection.

AT&TBell Laboratories in the United States managed to
send information at a rate of 420 megabits per second, over
161.5 km through an optical fibre cable. In Japan, 445.8
megabits per second was achieved over a shorter distance. At
this rate, the entire text of the Encyclopedia Britannica
could be transmitted in one second. Currently, AT&T is
working on a world network to support high volume data
transmission, international computer networking, electronic
mail and voice communications (a single fibre can transmit
200 million telephone conversations simultaneously).